Virgil crypto on Alpine linux v3.8

This article is a quick-start guide for debugging issues with the Virgil crypto library, Alpine Linux v3.8, and OpenJDK 1.8.

While testing different crypto libraries for a pet project, one candidate was Virgil. After a few hours of setup, I had a working prototype. Everything ran smoothly on macOS and Windows development machines, but things started breaking after deployment to Amazon.

The first clue came from the following exception, which suggested a problem loading libraries compiled by Virgil:

org.springframework.web.util.NestedServletException: Handler dispatch failed; 
nested exception is java.lang.NoClassDefFoundError: 
Could not initialize class com.virgilsecurity.crypto.virgilcryptojavaJNI

Further analysis showed that Virgil copies precompiled .SO to tmp directory: /tmp/virgil_crypto_java3134786209685506331.so.

Logical step was to list shared libraries virgl_crypto_java by executing the following command: ldd /tmp/virgil_crypto_java3134786209685506331.so

Output of the ldd command:

ldd (0x7f47776a8000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x7f4776fbc000)
libm.so.6 => ldd (0x7f47776a8000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x7f4776daa000)
libc.so.6 => ldd (0x7f47776a8000)
Error loading shared library ld-linux-x86-64.so.2: No such file or directory (needed by /tmp/virgil_crypto_java3134786209685506331.so)

Let's look at the following error message: Error loading shared library ld-linux-x86-64.so.2.

We need to figure out where ld-linux-x86-64.so.2 file resides. That can be checked the following website. We can see that libc6-compat needs to be installed. This can be done by running the command: apk add libc6-compat or by adding the following command to the docker file: RUN apk add --update --no-cache libc6-compat. By default, libc6-compat is not included, since Alpine Linux ships with the musl C library instead of glibc.

So everything should work now? Right? Well, yes, it worked until Alpine Linux released patch that broke the code. I've decided to check the Alpine linux git repository and stumbled upon the following commit - click here.

The problem with this commit is that previously /lib64 was just a symlink to the /lib directory. With this change, that is no longer the case.

As a result, ld-linux-x86-64.so.2 is copied to /lib64 instead of /lib, which breaks the code. A quick (and dirty) workaround is to manually copy the file to /lib (e.g. cp /lib64/ld-linux-x86-64.so.2 /lib/).